with the particulars respecting the states and processes in the ovule during the earliest life-stages of its development. The doctrines of the physiology of metabolism in men and beasts under different circumstances have exercised so powerful an influence over our comprehension of the relations of the individual during the sexual-life, that we practically find in all these teachings a powerful support, whence we may obtain many elucidations bearing upon the question lying before us, and may discover the principles necessary to complete our theory. But, before entering upon the fundamental principles of the theory which I have set forth, I wish to mention a treatise of Mayrhofer’s, the principal results of which I shall briefly recapitulate. After that I shall mention briefly such information as I have met with respecting the nutrition of the mother. Mayrhofer was led by critical notices and the observations of others, and, further, by his own experiences, to conclusions which he set forth in propositions, some of which I select here. In the plants and the lower animals food plays a principal part in the development of sex. The sex is not generated, but depends upon external influences over the fruit which is in a state of development. And here we have a stage which precedes the separate sex in man, in which stage sexual neutrality must be regarded as normal, where also we find a kind of hermaphroditism. Whether sex in the human species is determined at conception, or only develops itself afterwards, we must attempt to discover from obstetric experience. The twins and triplets contained by one chorion are of the same sex, and have a common placenta in which the blood passages of both umbilical cords communicate with one another. On this account, also, many opine that the identity of sex is occasioned by the intermixture of the blood, an opinion regarded, on the contrary, by others, with incredulity, because the intermixture of the blood might very possibly lead merely to a mixture and not to homogeneity, under which circumstances dissimilarity of development would be possible enough. We may here adduce the following facts also (Jhering): The armadilloes produce a number of young in one litter, which are normally developed in a single chorion, and are of the same sex, as in the case with man when twins are developed in one chorion.